1. Field of the Invention
This invention relates to a fiber grinding technique, more particularly, to a fiber grinding process and apparatus that employs a single-step grinding technique to asymmetrically shape an end face of an optical fiber.
2. Description of the Related Art
Nowadays, optical fibers have been used widely in daily activities of people, for instance, in transmitting images, voices, data, etc. Since optical fibers have the properties of high capacity, high quality and high speed, they have been substituted increasingly for conventional communication cables.
Referring to FIG. 1, a typical optical fiber 1 has a fiber end face 11 and a fiber core 12. The fiber end face 11 determines the coupling efficiency of the optical fiber 1. A high coupling efficiency means that the fiber end face 11 is capable of focusing efficiently into the fiber core 12 a light beam from a laser light 13 passing through the fiber end face 11.
Referring to FIGS. 2 and 3, there is shown a fiber end face polishing system 2 which is disclosed in Taiwanese Patent No. 1238097 entitled, “Optical Microlens polishing System and Method.” The system 2 includes a support 21, a fiber holder 22, a polishing unit 23 and a moving unit 24. The fiber holder 22 is mounted on the support 21 to hold an optical fiber 20. The polishing unit 23 has a resilient pad 231 and a polishing film 232 fixed to the resilient pad 231. The polishing film 232 contacts the optical fiber 20 to polish the end face thereof.
The moving unit 24 has first, second third step motors 241, 242 and 243 that serve to provide three motions of different directions. The first step motor 241 is used to provide a linear movement along a first axis (M1) for the fiber holder 22, i.e., along an axis of the optical fiber 20. The second step motor 242 rotates the fiber holder 22. The third step motor 243 is used to move and adjust the optical fiber to an inclined position.
In use, the optical fiber 20 held by the fiber holder 22 is first moved linearly along the first axis (M1) to a predetermined point, and is inclined with the polishing unit 23 by an appropriate angle (M2). Afterwards, the second step motor 242 causes the optical fiber 20 to rotate about the first axis (M1) so that the optical fiber 20 is polished by the polishing film 232 until the end of the optical fiber 20 has a predetermined end face.
Since the polishing system 2 employs three step motors which require different control parameters, the construction and operation of the entire system are complicated. In addition, while the polishing system 2 can form the optical fiber end face into a hemisphere, a circular cone, a wedge shape, or a quadrangular pyramid shape, it is unable to provide an optical fiber with an asymmetric fiber end face or microlens that has good coupling with a high power laser having a high aspect ratio.
A symmetic fiber microlenses have been fabricated in the art by employing a multi-step grinding process or a complicated laser micromachining process. The multi-step grinding process is complicated due to the use of multiple grinding steps. Furthermore, because the multiple grinding steps are employed, it is difficult to have control over small offset of fiber microlens (i.e., the eccentricity between the center of the optical fiber and the microlens) to form reproducible elliptical fiber end faces or fiber microlenses, thus resulting in low yield fabrication.